Unraveling the importance of forest structure and composition driving soil microbial and enzymatic responses in the subtropical forest soils

As the responsive soil properties, soil microbial fractions and enzymatic activities are often recommended for assessing soil environment. Different flora, silvicultural practices, and anthropogenic activities regulate essential ecosystem processes. They could substantially affect biological properties, nutrient budgets, and biogeochemical cycles at local and regional scales. This study examined how different forest compositions influenced by various anthropogenic activities (land use change, over-exploitation, species translocation) affect soil microbial properties and enzymatic activities, as well as the effects of soil chemical properties on these patterns in important sub-tropical forest ecosystems in Southern China. The research was conducted at Lutou forest research station, located in Yueyang, Hunan Province, China. Soil samples were collected at 0–10, 10–20, and 20–40 cm depths from natural broadleaved forest (NBF), coniferous monoculture plantations (CPF), and mixed forest stand. CPF stands are directly affected by human interference and frequent harvesting practices, whereas mixed forest and NBF stands are naturally grown forests with minimal human interference. Enzymes continually play a positive role in preserving soil health. The results showed that the interaction effect of forest type and soil depth significantly influenced urease, sucrase, and protease activity (all p < 0.001); however, no clear patterns were observed. Soil microbial carbon (MBC) and soil microbial nitrogen (MBN) were remarkably higher in 0–10 cm in mixed forest and NBF stand compared to CPF stand. For the upper soil layer, soil organic carbon (SOC) was higher in mixed forest, whereas, for the remaining two layers, it was observed to be highest in NBF. Moreover, the microbial quotient (MBC/SOC) was considerably higher in NBF forest in all soil layers than in mixed forest and CPF stand. Soil organic carbon (SOC) and soil total nitrogen (TN) had a strong positive relationship with MBC compared to MBN. Our study contributes toward an enhanced understanding of soil enzymatic responses and microbial soil dynamics’ biological patterns, controls, and activities in different rural forest ecosystems

The Effect of Co-Additives (Biochar and FGD Gypsum) on Ammonia Volatilization during the Composting of Livestock Waste

The effectiveness of co-additives for improving livestock waste composting (reduction of air pollution and conservation of nutrients) was investigated. Biochar and Flue gas desulphurization gypsum (FGD gypsum) were used to supplement the composting of a mixture of slaughter waste, swine slurry, and sawdust. Different compositions of additives (0% or 5% each, 10% biochar or FGD gypsum) were tested in triplicate on the laboratory scale. In addition, the effects of two different aeration schemes (continuous and intermittent) were also investigated. Ammonia volatilization, physicochemical characteristics, and compost maturity indices were investigated. The results indicated that the use of the co-additive (Biochar and FGD gypsum) during composting of livestock waste led to a reduction of ammonia volatilization by 26–59% and to a 6.7–7.9-fold increase of nitrate accumulation. The total ammonia volatilization of intermittent aeration treatment was lower than that of continuous aeration using co-additives treatment. It was concluded that co-additives (biochar and FGD gypsum) might be utilized in livestock waste composting to reduce ammonia volatilization and improve nutrient conservation

Effect of Biochar Amendments on the Co-Composting of Food Waste and Livestock Manure

The global increase in population will result in increased global food production which can, in turn, lead to excessive food waste. Although composting is widely adopted for the conversion of organic waste into value-added products, there are several limitations, such as its lower efficiency in composting food waste without co-composting, the loss of nutrients, and the emission of greenhouse gases. Due to its renowned characteristics, biochar amendments are used during composting to overcome these issues; each waste should be at an appropriate level to yield good quality compost with high nutrient levels. In this study, we co-composted food waste with chicken and swine manure with varying proportions in the presence and absence of biochar to identify the ideal proportion of each raw material and the biochar. Physicochemical parameters such as pH, EC, temperature, bulk density, porosity, C:N ratio, and gaseous emissions were analyzed. The results showed that the desired quality of compost was obtained in the treatment with 5% biochar with 40%, 20%, and 20% of food waste, chicken manure, and swine manure, respectively, and 15% sawdust

Assessment of nutrient quality, heavy metals and phytotoxic properties of chicken manure on selected commercial vegetable crops

Due to rapid expansion in the poultry industry, production of poultry manure has also consequently increased, resulting in unplanned disposal of this manure to the soil in some cases, with possible negative environmental consequences. In this study, 10 separate poultry manure samples were collected from different sites located in the central Eastern Cape, South Africa and characterized for chemical and phytotoxic properties. The poultry manures had an average neutral pH (range 6.94 − 7.97) whilst the electrical conductivity was highly variable from 2.45 dS/m to 12.3 dS/m between the 10 sites. The high conductivity values recorded in some of the manures indicate that caution may need to be practiced when directly applying these manure to the soil, to avoid buildup of soluble salts. All samples showed a very high concentration of total P (1963.1 mg/kg − 2644.1 mg/kg) with the plant available fraction ranging from 21.3% − 37.7% of the total P. All the heavy metals measured (Cr, Cu, Ni, Pb and Zn) were below the maximum permissible limits set by the U.S. Environmental Protection Agency. However, some of the poultry manure showed some level of phytotoxicity based on the plant bioassay, with some samples, recording a germination index less than 50% for the different crops evaluated. However, this bioassay may not be conclusive and there is need to evaluate this phytotoxicity in real world field applications as there is paucity of information on this aspect regarding poultry manure. Such filed studies can be used to evaluate alternative strategies such as planting and harvest intervals between application of these manures and planting or harvesting. It is also suggested that further biodegradation through composting or vermicomposting may be required to improve nutrient content and reduce the presence of phytotoxic compounds in some of the poultry manures before use as soil amendments

Modeling sertonin's contributions to basal ganglia dynamics in Parkinson's disease with impulse control disorders

Impulsivity involves irresistibility in execution of actions and is prominent in medication condition of Parkinson’s disease (PD) patients. In this chapter, we model a probabilistic reversal learning task in PD patients with and without impulse control disorder (ICD) to understand the basis of their neural circuitry responsible for displaying ICD in PD condition. The proposed model is of the basal ganglia (BG) action selection dynamics, and it predicts the dysfunction of both dopaminergic (DA) and serotonergic (5HT) neuromodulator systems to account for the experimental results. Furthermore, the BG is modelled after utility function framework with DA controlling reward prediction and 5HT controlling the loss and risk prediction, respectively. The striatal model has three pools of medium spiny neurons (MSNs) including those with D1 receptor ® alone, D2R alone, and co-expressing D1R-D2R neurons. Some significant results modelled are increased reward sensitivity during ON medication and an increased punishment sensitivity during OFF medication in patients. The lower reaction times (RT) in ICD subjects compared to that of the non-ICD category of the PD ON patients are also explained. Other modelling predictions include a significant decrease in the sensitivity to loss and risk in the ICD patients

An extended reinforcement learning model of basal ganglia to understand the contributions of serotonin and dopamine in risk-based decision making, reward prediction, and punishment learning

Although empirical and neural studies show that serotonin (5HT) plays many functional roles in the brain, prior computational models mostly focus on its role in behavioral inhibition. In this study, we present a model of risk based decision making in a modified Reinforcement Learning (RL)-framework. The model depicts the roles of dopamine (DA) and serotonin (5HT) in Basal Ganglia (BG). In this model, the DA signal is represented by the temporal difference error (δ), while the 5HT signal is represented by a parameter (α) that controls risk prediction error. This formulation that accommodates both 5HT and DA reconciles some of the diverse roles of 5HT particularly in connection with the BG system. We apply the model to different experimental paradigms used to study the role of 5HT: (1) Risk-sensitive decision making, where 5HT controls risk assessment, (2) Temporal reward prediction, where 5HT controls time-scale of reward prediction, and (3) Reward/Punishment sensitivity, in which the punishment prediction error depends on 5HT levels. Thus the proposed integrated RL model reconciles several existing theories of 5HT and DA in the BG

Modeling serotonin's contributions to basal ganglia dynamics

In addition to dopaminergic input, serotonergic (5-HT) fibers also widely arborize through the basal ganglia circuits and strongly control their dynamics. Although empirical studies show that 5-HT plays many functional roles in risk-based decision making, reward, and punishment learning, prior computational models mostly focus on its role in behavioural inhibition or timescale of prediction. This chapter presents an extended reinforcement learning (RL)-based model of DA and 5-HT function in the BG, which reconciles some of the diverse roles of 5-HT. The model uses the concept of utility function-a weighted sum of the traditional value function expressing the expected sum of the rewards, and a risk function expressing the variance observed in reward outcomes. Serotonin is represented by a weight parameter, used in this combination of value and risk functions, while the neuromodulator dopamine (DA) is represented as reward prediction error as in the classical models. Consistent with this abstract model, a network model is also presented in which medium spiny neurons (MSN) co-expressing both D1 and D2 receptors (D1R-D2R) is suggested to compute risk, while those expressing only D1 receptors ae suggested to compute value. This BG model includes nuclei such as striatum, Globus Pallidus externa, Globus Pallidus interna, and subthalamic nuclei. DA and 5-HT are modelled to affect both the direct pathway (DP) and the indirect pathway (IP) composing of D1R, D2R, D1R-D2R projections differentially. Both abstract and network models are applied to data from different experimental paradigms used to study the role of 5-HT: (1) risk-sensitive decision making, where 5-HT controls the risk sensitivity; (2) temporal reward prediction, where 5-HT controls timescale of reward predition, and (3) reward-punishment sensitivity, where punishment prediction error depends on 5-HT levels. Both the extended RL model (Balasubramani, Chakravarthy, Ravindran, & Moustafa, in Front Comput Neurosci 8:47, 2014; Balasubramani, Ravindran, & Chakravarthy, in Understanding the role of serotonin in basal ganglia through a unified model, 2012) along with their network correlates (Balasubramani, Chakravarthy, Ravindran, & Moustafa, in Front Comput Neurosci 9:76, 2015; Balasubramani, Chakravarthy, Ali, Ravindran, & Moustafa, in PLoS ONE 10(6):e0127542, 2015) successfully explain the three diverse roles of 5-HT in a single framework

A Mini-Review on Syngas Fermentation to Bio-Alcohols: Current Status and Challenges

Biomass gasification produces syngas, mainly comprised of CO and H2 along with H2S, CO2, N2, and tar compounds. Inorganic carbon present in syngas as CO and CO2 can be utilized for the production of several value-added chemicals including ethanol, higher alcohols, fuels, and hydrogen. However, chemical sequestration operates at a high temperature of 300–500 °C and pressure of 3–5 MPa in the presence of heavy metal catalysts. Catalyst regeneration and the maintenance of high temperature and pressure increased the cost of operation. Microorganisms like algae and bacteria including Acetobacterium and Clostridium also have the potential to sequester carbon from the gas phase. Research has emphasized the production of microbial metabolites with a high market value from syngas. However, scale-up and commercialization of technology have some obstacles like inefficient mass transfer, microbial contamination, inconsistency in syngas composition, and requirement for a clean-up process. The current review summarizes the recent advances in syngas production and utilization with special consideration of alcohol and energy-related products along with challenges for scale-up

Biosurfactants: Potential and Eco-Friendly Material for Sustainable Agriculture and Environmental Safety&mdash;A Review

With the present climate change and increasing world population, there is an urgent need to discover creative, efficient, and cost-effective natural products for the benefit of humanity. Biosurfactants are produced by various microorganisms that have several distinct properties compared to other synthetic surfactants, including mild production conditions, multifunctionality, higher biodegradability, and lower toxicity of living cells synthesis of active compounds. Due to their surface tension reducing, emulsion stabilizing, and biodegrading properties of these in place of chemical surfactants, they are generating huge demand in terms of research and usage. Biosurfactants are widely used in the food industry as food-formulation ingredients and antiadhesive agents as emulsifiers, de-emulsifiers, spreading agents, foaming agents, and detergents that find application in various fields such as agriculture, industrial sectors, and environmental recreation. Recent research focused more on heavy metal bioremediation from compost was achieved using biosurfactants-producing bacteria, which resulted in an improvement in compost quality. Although a number of studies on biosurfactants synthesis have been reported, very limited information on its cinematics and the consumption of renewable substrates are available. In this review paper, we made an attempt to critically review biosurfactants, their usage, research related to them, and challenges faced

Adsorption Characteristics of Ammonium Nitrogen and Plant Responses to Biochar Pellet

For feasibility of carbon sequestration as well as in the mitigation of greenhouse gases for application of biochar pellet, this experiment was conducted, focusing on the adsorption characteristics of NH4-N on biochar pellet mixed with different ratios of pig manure compost. For NH4-N adsorption on biochar pellets, the loading amount of biochar pellet was 211.5 mg in 50 mL of aqueous solution, and the adsorption fitted very well with Langmuir isotherm. The maximum adsorption and removal rates were 2.94 mg g&minus;1 and 92.2%, respectively, in the pellet that contained 90% of biochar. It was also observed, by kinetic models, that NH4-N was adsorbed fast on biochar pellet with a combination ratio of 9:1 of biochar pellet/pig manure. It was further observed that the higher the amount of biochar contained in the biochar pellet, the greater the adsorption of NH4-N. For the plant response observed for lettuce, it was shown that the leaf biomass in plots treated with a 9:1 biochar/pig manure compost increased by approximately 13% compared with the leaf biomass in plots treated with the compost alone. The leaf biomass of the other treatments was higher than that of the control. This implies that the application of biochar pellets, regardless of the biochar contents, might be useful for soil carbon sequestration and greenhouse gas mitigation for agricultural practices